1. Field of the Invention
The present invention relates generally to an indicating instrument for an automotive vehicle and more specifically to a mechanical indicating instrument mounted on an automotive vehicle, which is visible when the ignition switch is turned on but nonvisible when the ignition switch is turned off.
2. Description of the Prior Art
The indicating instruments for an automotive vehicle can be classified into two, mechanical and electrical types. In the mechanical indicating instruments, measured values are indicated by pointers. On the other hand, in the electrical indicating instruments, measured values are indicated by electric elements such as fluorescent character display tubes, light emitting diodes, liquid crystal displays, etc. alone or in combination.
In the case of the mechanical indicating instruments, the pointers and the dial are illuminated by external sunlight in the daytime and by a lamp or lamps disposed in back of the dial in the nighttime. On the other hand, in the case of the electronic indicating instruments of fluorescent character display tubes or light emitting diodes, these elements can emit light from the display surfaces thereof in the form of pattern irrespective of the daytime or nighttime.
Therefore, when the instruments are irradiated with external light, the mechanical instruments are well visible, but the instruments using display tubes or light emitting diodes are not well visible. Further, in the mechanical instruments, the pointers and dial can been seen whenever the passenger compartment is bright, even after the ignition switch has been turned off. On the other hand, in the light emitting instruments, since a dark material is placed in front of the display elements to unvisualize the light-nonemitting elements such as display tubes, resin casings, etc., when the ignition switch is off, the instrument face is black and therefore the driver cannot recognize the indicating instrument. However, when the ignition switch is turned on, only the indicator characters and/or symbols are instantaneously relieved against the dark background.
In summary, it is preferable that the indicating instruments for an automotive vehicle are dark and unvisible when the ignition switch is kept turned off, but clearly relieve quantities to be measured against the dark background.
The arrangement of the prior-art mechanical indicating instrument for an automotive vehicle will be described in further detail with reference to the attached drawings under DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS.